Safe crossings for amphibians in particular, are dependent on several factors: it is important for the length of the tunnel to be as short as possible; the material must not remove moisture from the animals; the temperature in the tunnel should be close to the ambient temperature; and to prevent any disorientation, the components should not contain any metal. The ACO Climate tunnel KT 500 satisfies all these factors because it is made of polymer concrete. This system can also easily cope with high groundwater levels and roads in cuttings.
Amphibians, reptiles and small mammals reach the entrance to the tunnel – the ACO Entrance unit – by following the guide wall system. Thanks to its internal width of 1000 mm and a variable height of 500–700 mm, the Entrance unit can be optimally adapted to suit the local topography. After installation in the embankment, the surface of the tunnel entrance unit aligns neatly at the same level as the top edges of the side walls.
The Entrance unit and the attached Climate tunnel or Climate stilt tunnel, form an integrated tunnel environment, fitted with slots at ground level which allow the internal temperature, relative humidity, ground moisture and light to adjust rapidly to the local outdoor conditions. These tunnels are therefore not affected by “central tunnel dryness” problems and also serve to reduce airflow through the tunnel. Climate tunnel elements without a slotted roof can be installed along some stretches such as under the main road traffic lanes. The surface layers close to the surface can be just 80 to 200 mm thick.
Polymer concrete is manufactured without cement or steel reinforcing. Polymer concrete is resistant to de-icing salt and many environmental chemicals. The water penetration depth into polymer concrete is zero. These are excellent properties for very long service life and ready acceptance by a range of small animals and particularly amphibians. The components have been tested to withstand the highest loads (400 kN) pursuant to EN 1433.